Data processing: generic control systems or specific application – Specific application – apparatus or process – Robot control
Reexamination Certificate
1999-08-16
2003-01-07
Nguyen, Thu (Department: 3661)
Data processing: generic control systems or specific application
Specific application, apparatus or process
Robot control
C318S568120
Reexamination Certificate
active
06505096
ABSTRACT:
TECHNICAL FIELD TO WHICH THE INVENTION RELATES
The present invention relates to a posture control system of a legged mobile robot, and specifically to a system for ensuring that a legged mobile robot, in particular a biped walking robot, reserves dynamic balance to maintain a stable posture, even when the robot is subject to unexpected object reaction force. More specifically, the present invention is most effectively applicable in a legged mobile robot having arms, and coordinately controls the arms and legs of the robot.
It should be noted that in this specification the term “object reaction force” is used to indicate the external force acting on the robot in a working environment including an object with which the robot is working, but excluding the floor reaction force acting on the robot from the contacting floor.
BACKGROUND ART OF THE INVENTION
A legged mobile robot, in particular a biped walking robot having arms, is known from, for example, “Development of a Biped Walking Robot Compensating for Three-Axis Moment by Trunk Motion” in vol. 11. No. 4, May 1993; “Journal of the Robotics Society of Japan”. The robot is provided with balance weights in the form of simplified arms. A desired gait is designed in advance using variables including anticipated gravity and inertial force to be generated by swinging the balance weights and robot walking is controlled to follow the designed gait.
In the prior art, however, the control is based on the premise that the arms are subject to no object reaction force. Therefore, if the control disclosed in the prior art is applied not only to walking, but also to working, the robot would be likely to lose dynamic balance, if it is subject to unexpected object reaction force from an object, resulting in the posture becoming unstable or, at worst, tipping over.
The applicant discloses a similar legged mobile robot in Japanese Laid-open Patent Application No. Hei 7 (1995)-205069 and proposes forcibly swinging robot arms to restore posture stability when the frictional force on the contact floor drops during walking.
In the control of legged mobile robot proposed therein by the applicant, however, the legs and arms are not controlled coordinately, but are separately or independently controlled. As a result, the robot may sometime lose dynamic balance due to the resultant force comprised of the force of gravity and inertial force generated by the arm swinging and reaction force from an object, thereby, contrary to what is expected, falling into an unstable posture.
A first object of the present invention is to solve the drawbacks of the prior art and to provide a posture control system for a legged mobile robot which can ensure to reserve dynamic balance or equilibrium so as to maintain a stable posture even when the legged mobile robot is subject to unexpected object reaction force.
A second object of the present invention is to provide a posture control system for a legged mobile robot which can effectively prevent the robot from tilting or tipping, even when the object reaction force changes abruptly, by displacing the position of center of gravity of the robot to a position at which the force is statically balanced.
A third object of the present invention is to provide a posture control system for a legged mobile robot which can maintain dynamic balance or equilibrium by properly changing the position of center of gravity of the robot and the floor reaction force even under a transit during which the displacement of position of center of gravity of the robot is in progress in response to the abrupt change of the object reaction force.
A fourth object of the present invention is to provide a posture control system for a legged mobile robot with arms which can reserve dynamic balance or equilibrium so as to maintain a stable posture, even when the robot arm is subject to unexpected gravity and inertial force or unexpected object reaction force when the robot arm is moved in a motion pattern not anticipated beforehand.
DISCLOSURE OF THE INVENTION
In order to achieve the above-mentioned objects, the present invention is configured to have a system for controlling posture of a legged mobile robot having at least a body and a plurality of links each connected to the body, comprising: desired gait predetermining means for predetermining a desired gait of the robot including at least a motion pattern including at least a desired trajectory of the body of the robot, a desired trajectory of floor reaction force acting on the robot, and a desired trajectory of external force other than the floor reaction force, acting on the robot; external force detecting means for detecting the external force other than the floor reaction force; external force difference determining means for determining an external force difference between the detected external force other than the floor reaction force and the external force of the desired trajectory; a model expressing a relationship between perturbation of the floor reaction force and perturbation of at least one of a position of center of gravity and a position of the body of the robot; model input amount determining means for determining a model input amount to be inputted to the model based on at least the determined external force difference; desired body trajectory correcting amount determining means for operating to input the model input amount to the model and based on a perturbation amount of at least one of the position of center of gravity and the position of the body obtained therefrom, for determining a desired body trajectory correcting amount, which corrects the desired trajectory of the body; desired floor reaction force trajectory correcting amount determining means for determining a desired floor reaction force trajectory correcting amount, which corrects the desired trajectory of the floor reaction force, based on at least the determined model input amount; and joint displacing means for displacing joints of the robot based on at least the determined desired body trajectory correcting amount and the desired floor reaction force trajectory correcting amount.
It should be noted here that the “position” is used to indicate, except for the position of gravity, the “position and/or posture”. The “posture” indicates the orientation or direction in the three-dimensional space as will be stated later.
It should be noted here that the “desired trajectory of floor reaction force” is used to indicate, more specifically, a desired trajectory of a central point of floor reaction force. It should also be noted that “corrects the desired trajectory of the floor reaction force” is used to indicate, more specifically, correction of the moment about the central point of floor reaction force.
It should further be noted here that “detecting the external force” is used to mean not only to detect, but also to estimate with the use of a disturbance observer.
It is configured in the system, the model input amount determining means includes: equilibrium center of gravity position perturbation amount determining means for determining a perturbation amount of an equilibrium position of the center of gravity at which the external force is statically balanced; and wherein the model input amount determining means determines the model input amount such the model converges to the perturbation amount of equilibrium position of the center of gravity.
It is configured in the system, the model is a model which approximates the robot by an inverted pendulum.
It is configured in the system, the equilibrium center of gravity position perturbation amount determining means includes: a limiter which limits the determined perturbation amount of equilibrium position of center of gravity within a predetermining range.
It is configured in the system, the desired floor reaction force trajectory correcting amount determining means includes: a limiter which limits the determined desired floor reaction force trajectory correcting amount within a predetermined range.
It is configured in the system, the desired trajectory of the floor reaction f
Hasegawa Tadaaki
Matsumoto Takashi
Takenaka Toru
Arent Fox Kintner Plotkin & Kahn
Honda Giken Kogyo Kabushiki Kaisha
Nguyen Thu
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